elmSunPosCalc/writegeolocations.html at master · jarmol/elmSunPosCalc · GitHub

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<!DOCTYPE html>
<html>
<head>
   <title>Distances and Bearings</title>
</head>
<body>
<div style="margin: 5%; font-size: 125%">
<h2 style="color: blue">The shortest distances between locations</h2>

<script>
showCity("Helsinki", 60.167, 24.95, "New York", 40.717, -74.0167);
showCity("Helsinki", 60.167, 24.95, "London  ", 51.500, 0.133);
showCity("Helsinki", 60.167, 24.95, "Berlin", 52.517, 13.383);
showCity("Helsinki", 60.167, 24.95, "Wien", 48.217, 16.367);
showCity("Helsinki", 60.167, 24.95, "Tallin", 59.433, 24.750);
showCity("Helsinki", 60.167, 24.95, "Stockholm", 59.333, 18.067);
showCity("Helsinki", 60.167, 24.95, "Tokyo", 35.683 , 139.70);

function showCity(city1, latit1, longit1, city2, latit2, longit2)
{
    document.write("<p>City " + city1
    + " ( Latitude " + latit1 + '&deg;'
    + " Longitude " + longit1 + '&deg; )');
    document.write('<p> City ' + city2
    + " ( Latitude " + latit2 + '&deg;'
    + " Longitude " + longit2 + '&deg; )');

    dist = haversine(latit1, longit1, latit2, longit2);

    document.write('<p> Distance from ' + city1 + " to "
            + city2 + ' ' + dist);

    bearing = newBearing(latit1, longit1, latit2, longit2);
    document.write('<p> Initial bearing ' + bearing);

    backBear = newBearing(latit2, longit2, latit1, longit1);
    document.write('<p> Back bearing ' + backBear);
    document.write("<hr>")
}


function haversine(lat1, lon1, lat2, lon2)
    {
        // distance between latitudes
        // and longitudes
        let dLat = (lat2 - lat1) * Math.PI / 180.0;
        let dLon = (lon2 - lon1) * Math.PI / 180.0;

        // convert to radians
        φ1 = lat1 * Math.PI / 180.0;
        φ2 = lat2 * Math.PI / 180.0;

        // apply formulae
        let a = Math.pow(Math.sin(dLat / 2), 2) +
                Math.pow(Math.sin(dLon / 2), 2) *
                Math.cos(φ1) *
                Math.cos(φ2);
        let radius = 6371; // Earth radius km
        let c = 2 * Math.asin(Math.sqrt(a));
        let dist = radius* c;
        distFix1 = parseFloat(dist.toFixed(1));
        return distFix1 + " km"
    }

function newBearing(lat1, lon1, lat2, lon2) {
    let radians = (v) => v*Math.PI/180;
    let φ1 = radians(lat1);
    let φ2 = radians(lat2);
    let λ1 = radians(lon1);
    let λ2 = radians(lon2);
    let  y = Math.sin(λ2-λ1) * Math.cos(φ2);
    let  x = Math.cos(φ1)*Math.sin(φ2) -
         Math.sin(φ1)*Math.cos(φ2)*Math.cos(λ2-λ1);
    let  θ = Math.atan2(y, x);
    var g = (θ*180/Math.PI + 360) % 360; // in degrees

    var wordHeading = ""
        if (g >  30 && g <  60) wordHeading = "North-East ↗️ "
        if (g >  60 && g < 120) wordHeading = "East ➡️ "
        if (g > 120 && g < 150) wordHeading = "South-East ↘️ "
        if (g > 150 && g < 210) wordHeading = "South ⬇️ "
        if (g > 210 && g < 240) wordHeading = "South-West ↙️ "
        if (g > 240 && g < 300) wordHeading = "⬅️  West"
        if (g > 300 && g < 330) wordHeading = "North-West ↖️ "
        if (g > 330 && g < 360) wordHeading = "North ⬆️ "
        if (g >=  0 && g <  30) wordHeading = "North ⬆️ "

    return (parseFloat(g.toFixed(2)) + '° ' + wordHeading);
}

</script>

<ul>
    <li><a href="https://www.movable-type.co.uk/scripts/latlong.html">About bearings and distances</a></li>
    <li><a href="https://www.timeanddate.com/worldclock/distanceresult.html?p1=101&p2=179">Compare this!</a></li>
</ul>
</div>
&copy; J. Lammi 2023
</body>
</html>